Preserving mankind's past from mother nature's quakes

Civil engineers are in a continuous search of non-destructive measurement techniques that can help to estimate structural condition. The high definition surveying (HDS) or laser scanning, from Leica Geosystems fulfils this need.

A joint research team comprised of members from UC Berkeley’s Structures Laboratory (a research lab specialising in full-scale structural testing and numerical analysis), Miyamoto International (an earthquake and structural engineering firm in the USA), Smart Scanning Solutions, LLC (a 3D scanning and modelling service provider in Uzbekistan) and BNZ (Leica Geosystems’ representative in Uzbekistan) has been deploying HDS reality management technology at heritage monuments along the historic Silk Road within Uzbekistan. Multiple monuments have been captured and analysed for earthquake susceptibility.

The beginning: assessment of natural decline

作为许多遗产纪念碑的代表性例子，选出了乌兹别克斯坦撒马尔罕的雷吉斯坦广场合奏团。合奏包括1417-1420的Ulugh Beg Madrasah，Sher-Dor Madrasah，1619-1636，Tilya-Kori Madrasah和Mosque，1646-1660，以及18世纪的Chorsu Domed Market。

Earthquakes, extreme seasonal temperatures, normal depreciation of the buildings and the economic crises of the 18th and 19th centuries have left the ensemble in a ruined condition. Structural repairs and straightening of the minarets had been conducted in 1923 and 1932; however, major restoration works were undertaken in recent years.

从70多个电视台扫描了该合奏，并带有Leica扫描仪。除了位于合奏中的所有古迹的全球尺寸外，扫描还捕获了纪念碑的所有细节：瓷砖形状和尺寸，它们在古迹中的整体位置，任何缺陷以及门廊的整体几何形状。为了达到点密度的细节，所有扫描的密度为2 mm x 2 mm。

The scan data produced extremely valuable results to be used in the decision making of further restoration strategies for the monument located in this earthquake-prone area of Central Asia. In generation of finite element models from the point cloud, Leica Cyclone software was used for surfaces with complex geometry.

“With the ScanStation's ability to achieve ultrahigh scan speeds, we were able to quickly collect the data needed for a thorough investigation of the monuments,” said Liliya Myagkova, Smart Scanning Solutions CEO. “And气旋’s simple registration enabled the team to process the point clouds for fast analysis.”

其中一个倾斜的尖塔的点云为有关结构中倾斜度的问题提供了答案。基于对点云的分析，获得了4.6％的倾斜度估计值。尖塔的原始锥度估计为2.3％。

激光扫描的新探险和监视

The laser scanning expeditions were expanded into new cities. An extensive list of historic structures included many cities of Uzbekistan: Bukhara, Shakhrisybaz and Tashkent. In addition to that, more historic structures in Samarkand were scanned.

Shakhrisyabz位于乌兹别克斯坦撒马尔坦以南约80公里处的乌兹别克斯坦南部。它曾经是中亚的主要城市，今天主要被称为14世纪Turco-Mongol Conqueror Timur的发源地。扫描的纪念碑，库克·古巴兹（Kuk Gumbaz）（蓝色圆顶）清真寺，来自帖木儿王朝时代，在联合国教科文组织世界遗产名单上。这座纪念碑建于1437年，几个世纪以来，经历了几项修复和加强工作。

The historic monument was scanned from 13 stations with aLeica ScanStation C10. Data registration was performed in Cyclone and error did not exceed 3 mm for all scans used in the final registration. The monument was scanned from outside, inside of the main hall, and inside of a stairway with a large crack between the portal and the main structure.

“With Uzbekistan’s extreme continental climate, the research team needed to ensure it could rely on the instruments. As the C10 can work in temperatures anywhere from -20 to +50 degrees Celsius, it was ideal for this project,” said Brian Quigley, BNZ director. “The full 360° x 270° field of view also ensured scanning the complex surfaces of the monuments would capture all features and make the process simpler for the researchers.”

对纪念碑的云云进行了调查。研究了主要门户，该门户从穿过两个码头底部的垂直平面的倾斜度进行了研究。该门户的倾斜度从南向北增加，最大差分位移在顶部的北角0.6 m。为了确保该门户网站的这种倾向不进行，建议对激光扫描进行定期监测。还建议继续安装激光靶标，以提高监测的准确性。永久安装的目标提供了在不同时间收集的点云之间进行一致的比较。

The geometry of the finite element model was generated from the point cloud. All major imperfections and existing reinforcements were included into the geometry of the model. Numerical modelling and subsequent analysis was conducted in specialist software SAP2000.

Since there is a very large variability in the material properties of masonry walls, material tests were conducted on a brick recovered from the site. The material properties were used within the software for accurate modelling.

chec的尖塔是在不同的时间扫描k if the inclination is progressing over time. The first scans were conducted by theScanStation C10第二点云是由P系列扫描仪收集的。第一次扫描已在旋风中进行了第二次扫描。在每个高程中，倾斜度估计为矢量，并具有方向性和价值。后一个结果使用了高清激光扫描的主要优势，该扫描捕获了表面的多个点，而其他方式无法通过其他方式获得。

进一步保护的未来研究

The test projects won interest from, and collaboration with, the Uzbekistan authorities dealing with heritage buildings. This provided permissions for the additional heritage scanning along Uzbekistan's active seismic zones in Samarkand, Bukhara, Tashkent and Shakhrisyabz.

With HDS scanning combined with material testing, advanced calibrated models were produced, accounting for brick properties, current conditions, and previous structural reinforcements. Long-term monitoring is being strategised and conservation recommendations are being provided based on the research data, including the investigation of dampening devices at an active mosque with multiple structural concerns.

“Laser scanning helps us to capture structural anomalies of historical artefacts so we can help protect them for future generations,” said Amir Gilani, Miyamoto International, Manager of Earthquake Engineering Department. “Without this advanced technology, it would be challenging to get the as-found geometry of historic structures with accuracy of few millimetres that is essential for structural analysis.”

为了认识到团队收集的数据的努力和价值，点云被接受到Cyark 500挑战数据库中，这是一项国际努力，以分类和存档濒临灭绝的文化遗产。